The present invention relates to a pickup unit for electric string instruments and more particularly relates to improvement in generation of bass range tones by electric string instruments such as electric guitars.
An electric string instrument is generally equipped with a pickup unit which detects string vibrations for conversion into corresponding electric signals. Piezoelectric elements are broadly used for such pickup units as disclosed in Japanese Utility Model Laid-open Hei. 2-27199.
In the construction of the pickup unit of this earlier proposal, a metallic bridge is mounted to a bridge base of an electric guitar to support thereon a metallic string holder. The string holder per se is often called as a bridge too. The string holder holds a plurality of strings arranged in tension on the bridge base. A bimorph type piezoelectric assembly is clamped directly between the string holder and the bridge.
The bimorph type piezoelectric assembly is made up of a pair of piezoelectric sheets clamping a metallic board which forms a common positive electrode. Since the piezoelectric assembly is clamped directly between the bridge and the string holder, string vibrations can be transmitted to the piezoelectric assembly from the string holder without any damping effect. This direct transmission system assures highly sensitive detection of the string vibrations with a high degree of fidelity.
Despite such an ideal detection of string vibrations, the pickup unit of this earlier proposal is unable to successfully detect bass range tones which are generated via body vibrations of an electroacoustic guitar. In order to cover this deficit, it is proposed to arrange a guitar microphone, i.e. an acoustic sensor, within the body of an electroacoustic guitar. This acoustic sensor picks up vibrations of the surface board of the electroacoustic guitar. With increase in volume of tones generated at a guitar amplifier, however, the body of the acoustic sensor tends to resonates with body vibration of the electroacoustic guitar, thereby inevitably causing harsh howling.